I. Field of the Invention
The present disclosure relates to methods and systems for determining the position of a mark made by an object such as a ball or other object on a playing surface during a sporting event, particularly in situations where the mark may not be visible to the naked eye. The present disclosure also relates to methods and systems for determining the trajectory of a ball or other object, based in part on the position of the mark left by the ball on the playing surface.
II. Background Information
Officiating referees, judges and umpires in many sports, including tennis, cricket, soccer and baseball, have a need for a technological solution to assist in making boundary judgments in accordance with the rules of the sport.
Many concepts and attempts have been made in the past to develop systems for making or assisting in boundary judgments. These systems include electronic circuits buried into or applied on the playing surface, radar and other remote-sensing apparatus, and cameras. These methods have provided limited success at best, often at a high cost.
Generally, current commercial systems track the ball in flight and estimate its impact position relative to a system of coordinates that are determined through a process of prior calibration and measurement. Such systems only provide an indirect estimate of whether the ball touched a feature of the playing surface.
For example, professional Tennis has recently introduced a “challenge” system that allows the use of technology to determine a line call. This system requires an exceptionally difficult alignment of cameras relative to the tennis court lines. The system tracks the flight path of the tennis ball from the multiple camera images and estimates the impact point of the ball on the court surface. This system has caused considerable controversy due to reports that it sometimes makes incorrect judgments. Accordingly, current systems that estimate where a ball lands are flawed, and may actually increase the risk of an incorrect call rather than guard against it.
Another consideration is that the boundaries in the game often comprise lines that are painted or applied to the surface(s) of the court or field. These lines are usually not perfectly straight nor do they have constant width. The referee or umpire in the sport (e.g. in Tennis) is required to apply the rules relative to the actual lines, however imperfect they may be. Therefore, a system that relies on tracking the ball in a chosen framework of spatial coordinates needs to “know” every part of the line in great detail. To measure the lines of a sporting venue to this level of detail, for use in a ball-tracking solution, is an impractical quest at present. Conventional tracking/navigation type systems therefore provide results that are often contested.
In addition, in many sports, the ball and/or surface may deform. Further, the ball may skid and roll during the period of contact. Therefore, the notion of a singular impact point or position is flawed for many practical ball games. Because the mark of the ball on the surface is variable, it should be taken into account when deciding if a line was touched or not. A system that tracks the ball and predicts impact points relies on estimates of the ball mark. A typical system as used currently estimates an ellipsoidal mark. Considering that a judgment must be made on whether a line was touched by the ball or not, methods to estimate the track and mark of the ball cannot be a reliable indicator of a boundary infringement.